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Biomedical subjects

E M Roberts

Publications and source records attributed to E M Roberts.

At least 37 records · Page 2Linked to original sources
PubMed1983

Quantification of intersegmental reactions during rapid swing motion.

A simple mathematical model was developed to quantify the non-muscular reactions between two adjacent segments undergoing rapid free-segment motion. Newtonian equations of motion were used to simulate the trajectories of the two segments using the input parameters of linear acceleration and muscular moment acting only about the proximal end of the proximal link. The intersegmental muscular force and moment were mathematically considered to be zero, and no constraints were placed on the motion of the two segments. The motion of the thigh and shank during the swing phase of running was simulated by the model and compared to the real motion obtained from cinematographic records. The simulation demonstrated that proximal thigh motion has a significant effect on the distal shank motion. Depending on the initial conditions, intersegmental reactions alone can produce large increases in distal segment speed. The role of the knee musculature in preventing these reactions during the swing phase of running was inferred.

Biomechanical Phenomena↗
PubMed1983

Spline solution to terminal zero acceleration problems in biomechanical data.

An augmented cubic spline function was evaluated as an alternative solution to the end-point problem which frequently arises in the smoothing and differentiation of biomechanical position-time data. The usual procedures of natural cubic spline functions and digital filtering have the undesirable effect of forcing the accelerations to zero at the ends of the data set. The proposed augmented cubic spline procedure does not have this characteristic but rather requires the curve to pass through a single extra point at each end of the data set. Using two different criteria with large acceleration magnitudes near the end of the data set, we have compared the effectiveness of all three methods in terms of the total curve (root mean square error) and in terms of the last few points (percent and algebraic error). In both experiments the augumented cubic spline procedure was found to be superior to both digital filtering and natural cubic spline functions. It was concluded that this technique could be used for smoothing and differentiating biomechanical data in instances where the underlying function is unknown and the accelerations at the end points of the data set are suspected of being non-zero.

Biomechanical Phenomena↗
PubMed1981

Pseudomonas maltophilia bacteremia in children undergoing open heart surgery.

Pseudomonas maltophilia was isolated from intraoperative blood cultures in eight of 13 children undergoing open heart surgery during a five-week period. Antibiograms were identical and included resistance to prophylactic antibiotics. The source of the outbreak was traced to contamination of both the calibration device used on the pressure monitoring system and the sensor surface of transducers used in this system. In a mock system, calibration with a contaminated device resulted in recovery of the organism from transducer dome fluid. Dye studies confirmed the integrity of the transducer membrane but demonstrated reflux of dome fluid into the monitoring line fluid. A case-control study revealed no patient- or surgery-related factors predisposing to P maltophilia bacteremia and no excess of morbidity or mortality in patients as a result of bacteremia. The outbreak was confined to patients undergoing open heart surgery and was terminated abruptly by sterilization of transducers and revision of the calibration device.

Cardiac Surgical Procedures↗
PubMed1981

Relationship between doses of prostaglandin F2alpha and stages of the breeding season for synchronization of estrus and ovulation in ewes.

Two experiments were conducted to compare estrous response to three doses (8, 16 and 24 mg) of prostaglandin F2alpha (PGF2alpha) administered by intramuscular injection to ewes between day 6 and 12 of the estrous cycle (Experiment I) and to ewes on unknown days of the estrous cycle during four different stages of the breeding season (Experiment II). In experiment I, a total of 41 ewes were treated with PGF2alpha. The injection of 24 mg PGF2alpha resulted in a higher proportion of ewes exhibiting estrus (13/14, 92.9%) within 5 days after treatment as compared to the other two doses (2/12 and 10/15, for 8 and 16 mg PGF2alpha, respectively). However, there was no significant difference for the proportion between 16 mg and 24 mg PGF2alpha. In experiment II, PGF2alpha was given to ewes on the 3rd of February (early breeding season), the 28th of February (mid-early breeding season), the 10th of April (mid breeding season) and the 27th of May (late breeding season). These was a significant difference for the proportion of ewes exhibiting estrus between the early breeding season and the other three seasons (P<0.05) but not for ewes ovulating. Throughout the breeding season, 16 mg PGF2alpha appeared to be slightly better than the other two doses (8 and 24 mg) although there was no overall difference in the estrous responses to treatment among the three doses. However, a significant difference in the proportion of ewes ovulating was found among the three doses of PGF2alpha (P<0.05). Especially, 16 mg PGF2alpha was significantly superior to 8 mg (P<0.01) and 24 mg (P<0.05). It was considered that there was a complicated relationship between the doses of PGF2alpha and the stages of the breeding season for induction of estrus and ovulation in the ewe.

Journal Article↗
PubMed1978

Effect of thymine concentration on cell shape in Thy- Escherichia coli B/r.

Cells of a thymineless mutant of Escherichia coli B/r are shown to change their shape when the concentration of thymine in the growth medium is reduced. Electron micrographs of whole cells and isolated sacculi were used to make quantitative measurements of the changes in cell length and width which occur as a result of such a change in thymine concentration. The results showed that there is an increase in cell volume, which is due to an increase in cell width accompanied by a decrease in cell length. These changes were compared with the predictions of models which assume that cell shape is influenced by the chromosome replication cycle.

DNA, Bacterial↗
PubMed1978

Lower extremity forces and torques during systematic variation of non-weight bearing motion.

Component and resultant external forces and torques at ankle, knee, and hip joints of unrestrained lower extremity motion were computed as resultant limb velocities were systematically changed. Cinematographic and modeling techniques were used to analyze 45 trials of five skilled soccer players who performed slow, medium and fast velocity kicks. A model of the lower extremity was incorporated, with kinematic data and segment mass estimates, into computer programs to quantify the mechanical variables. Monotonic increases in magnitudes of all kinetic elements occurred as the velocity of kicking was increased. Significant differences were also observed in the maximum values of the net parallel and perpendicular external force actions, and resultant torques at the joints with changes in limb velocity.

Ankle↗
PubMed1976

Tissue inactivation of slow reacting substance of anaphylaxis.

The release of slow reacting substance of anaphylaxis (SRS-A) from sensitized guinea-pig lung challenged with antigen was followed by a fall in the activity of this mediator in the diffusate when the incubations were continued for 3 h. The inactivating principle was also present in normal lung in addition to other normal guinea-pig tissues such as the liver, kidney, spleen, ileum and skin. No acitivity was found in muscle. Evidence is provided that some of this SRS-A-inactivating activity was due to tissue arylsulphatases. These were measured by hydrolysis of p-nitrophenyl sulphate (p-NPS) and p-nitrocatechol sulphate (p-NCS), which reflect activities of arylsulphatase II A and II B respectively. Hydrolytic activity for p-NCS was present in all tissues with SRS-A-inactivating properties, whereas only lung, liver and skin tissue hydrolysed p-NCS and p-NPS. Following passage of a cell-free lung homogenate through a column of Sephadex G-200 the p-NCS hydrolysing and SRS-Z-inactivating activities eluted together, with molecules having a molecular size of approximately 150,000 Daltons, p-NPS hydrolysing activity being destroyed during the preparation of the homogenate. The release of arylsulphatase from sensitized tissue was not dependent on the presence of specific antigen. These experiments suggest that inactivation of SRS-A is related to tissue arylsulphatase and that these enzymes may play a role in the expression of the effective levels of this mediator within the tissues.

Animals↗